diff --git a/testing/src/Environment.php b/testing/src/Environment.php
index 2fa8119e..b14fd8ba 100644
--- a/testing/src/Environment.php
+++ b/testing/src/Environment.php
@@ -56,7 +56,7 @@ public static function create(?Command $command = null): self
     /**
      * @param array<string, mixed> $envs
      */
-    public function start(?array $rrCommand = null, int $commandTimeout = 10, array $envs = [], string $roadRunnerConfigFile = '.rr.yaml'): void
+    public function start(?string $rrCommand = null, int $commandTimeout = 10, array $envs = [], string $roadRunnerConfigFile = '.rr.yaml'): void
     {
         $this->startTemporalTestServer($commandTimeout);
         $this->startRoadRunner($rrCommand, $commandTimeout, $envs, $roadRunnerConfigFile);